chore: import upstream snapshot with attribution

tests/unit/plugins-manager.test.ts

@@ -0,0 +1,51 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+
+// Manager is a singleton that depends on DB, scanner, and loader.
+// We test the module structure and type contracts here.
+// Full lifecycle tests require integration setup with SQLite.
+
+import { pluginManager } from "../../src/lib/plugins/manager.ts";
+
+// ── Singleton ──
+
+test("pluginManager is a singleton", () => {
+  const a = pluginManager;
+  const b = pluginManager;
+  assert.strictEqual(a, b);
+});
+
+test("pluginManager has all lifecycle methods", () => {
+  assert.equal(typeof pluginManager.install, "function");
+  assert.equal(typeof pluginManager.activate, "function");
+  assert.equal(typeof pluginManager.deactivate, "function");
+  assert.equal(typeof pluginManager.uninstall, "function");
+  assert.equal(typeof pluginManager.scan, "function");
+  assert.equal(typeof pluginManager.loadAll, "function");
+  assert.equal(typeof pluginManager.getLoaded, "function");
+  assert.equal(typeof pluginManager.listAll, "function");
+  assert.equal(typeof pluginManager.getPlugin, "function");
+});
+
+test("pluginManager.getLoaded returns undefined for unknown plugin", () => {
+  const result = pluginManager.getLoaded("nonexistent-plugin");
+  assert.equal(result, undefined);
+});
+
+test("pluginManager.install throws for invalid directory", async () => {
+  await assert.rejects(
+    () => pluginManager.install("/nonexistent/path"),
+    (err: Error) => {
+      assert.ok(err.message.includes("No valid plugin found"));
+      return true;
+    }
+  );
+});
+
+test("pluginManager.activate throws for unknown plugin", async () => {
+  await assert.rejects(() => pluginManager.activate("nonexistent-plugin"));
+});
+
+test("pluginManager.uninstall throws for unknown plugin", async () => {
+  await assert.rejects(() => pluginManager.uninstall("nonexistent-plugin"));
+});